Lawyers acting for Mr Namah filed a summons with PNG's National Court on Friday.

The injunction seeks to have the current detainees released and to prevent the government from receiving or detaining any more asylum seekers from Australia.

Mr Namah said in a statement that he regretted taking the action against the PNG government, but he believed the processing centre was unconstitutional.

"The ministers of the O'Neill-Dion government have now received a summons to appear and defend their conduct in the National Court," he said in the statement.

Mr Namah said the detainees on Manus were being held illegally in PNG.

"We will take this matter as far as necessary to ensure that the values of our nation's constitution are upheld," he said.

"This legal challenge also attempts to remedy the many abuses of PNG law and of ministerial powers which have given rise to the situation on Manus."

He said the opposition challenged the right of the government to force people seeking refugee status in Australia to enter PNG, where they were being held "illegally and indefinitely under inhumane conditions".

The motivation for the court challenge has also drawn comment in Australia.

A NOTE ABOUT RELEVANT ADVERTISING: We collect information about the content (including ads) you use across this site and use it to make both advertising and content more relevant to you on our network and other sites.